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Forensic Serology

Forensic Serology

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Forensic Serology

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  1. Forensic Serology Chapter 8

  2. Blood Components • Plasma--fluid part of blood unclotted blood • Erythrocytes—hold hemoglobin and transport oxygen • Leukocytes—immune cells • Platelets--clotting • Serum—yellow fluid that remains after clotting of blood, mostly water + dissolved substances (proteins, ions, etc)

  3. Antigen and Antibodies • Blood Type A has A antigens and B antibodies • Blood Type B has B antigens and A antibodies • Blood Type AB has both A and B antigens and no antibodies • Blood Type O does not have any antigens but both A and B antibodies • Positive blood has Rh(D) antigens = Rh+ • Negative blood does not have Rh(D) antigens but has D antibodies = Rh-

  4. Serology • Positive blood will agglutinate with Anti D serum • Negative blood will not agglutinate with Anti D serum • A blood will agglutinate with Anti A serum • B blood will agglutinate with Anti B serum • AB blood will agglutinate with both anti A and anti B serum • O blood will not agglutinate with anti A or anti B • http://www.youtube.com/watch?v=E0d5Qx42vmQ

  5. Paternity Testing with Blood Type • A Blood Type—AA or AO • B Blood Type—BB or BO • O Blood Type—OO • AB Blood Type—AB • Parent gives each offspring one of two alleles

  6. Immunoassay techniques • Used to detect drugs in blood and urine • Animals are injected with proteins with drug antigens—animal makes drug detecting antibodies that can be harvested • Presumptive drug testing with these cultured antibodies can be used to detect opiates, cannabinoids, cocaine, amphetamines, phencyclidine, barbituates and methodone

  7. Producing Antibodies • Radioimmunoassay (RIA)—uses radioactive tags to find drugs • Enzyme-Multiplied Immunoassay Technique (EMIT)—fast and used with urine; adds antibodies to urine that bind to specific drugs • Polyclonal and Monoclonal Antibodies—animals produce many different antibodies when exposed is polyclonal; scientists need one kind of antibody (monoclonal; fused with cancer cell to make hybridoma cell

  8. Blood Stain Analysis • 3 Questions • Is it blood? • Is it human? • Can it be matched closely to a particular person?

  9. Presumptive Color Testing • Benzadine color test—use has been reduced because it is a carcinogen; measures for presence of hemoglobin • Kastle-Mayer—uses phenolphthalein as an indicator, and hydrogen peroxide to cause the conversion of catalase to give pink color; will test positive with samples with catalase (animal and some plant material) • http://www.youtube.com/watch?v=6Ex0Fd_PDhU

  10. Luminol • Presumptive blood test • Reaction with blood emits light that can be seen in darkened area • Sprayed on area, turn dark, emits blue light • http://www.youtube.com/watch?v=hbEHvRrfqrc

  11. Microcrystalline Tests • Takayama test • Teichmann tests • Add chemicals to blood that causes hemoglobin-containing crystals to form • Susceptible to contaminants and less sensitive that color tests

  12. Precipitin Test • Used to determine if blood stain is human or from animal • Grow antibodies to human blood in rabbit; use antibodies to test for presence of human antigens; Human antiserum • Rabbits can be used to make antibodies against various animal bloods as well

  13. Gel Diffusion • Use agar gel—antibodies and antigens come together in medium plate • Blood and human antiserum are loaded into wells • Precipitant forms if blood is human between two wells

  14. Blood Spatter • Important Blood Qualities to Interpret Blood Spatter • Surface texture—more spatter with softer, porous material • Direction of travel—pointed end faces direction of travel • Impact angle—right angle yields circular stain • Origin of spatter—draw lines through many spatter points; point of intersection is origin of spatter • http://www.youtube.com/watch?v=Od8YuwUT794

  15. Forensic Analysis of Semen • Tests for Presence of Semen • Acid Phosphatase Stain—acid phosphatase is made by the prostate gland and added to semen during ejaculation; presence can be detected by acidic sodium alpha napthylphosphate and fast blue dye or 4-methyl umbelliferyl phosphate (will fluoresce) • Microscopic examination—look for presence of sperm cells • Prostate specific antigen—polyclonal antibodies grown in rabbits used to bind to p30 protein or prostate specific antigen

  16. Rape Evidence Collection • Rape Kit Collection from victims • Hair samples: head, pubic, body • Body opening swabs: vagina, anus, mouth • Blood sample • Fingernail scrapings • All clothing • Urine sample • Collected from male suspects • All clothing • Hair: head, pubic, and body • Genital swab • Blood sample • Cheek cells